Fabrication and Characterization of Dense Na3Zr2Si2PO12 (NZSP) Ceramics Synthesized Via Solution Combustion Method for All Solid Sodium-Ion Battery

Abstract

Sodium ion batteries (SIBs), relying on highly abundant sodium, present a compelling alternative to lithium-ion batteries with superior electrochemical performance, a broad operating temperature range, and rapid charging capabilities. However, liquid electrolytes with electrochemical instability and low ion selectivity in SIBs can lead to leakage concerns. As a solution, the NASICON-type solid-state electrolyte, Na3Zr2Si2PO12 (NZSP), emerges as a potential candidate for all-solid-state Na batteries, aiming to replace traditional liquid electrolytes used in Na-ion batteries. Solid-state synthesis of Na3Zr2Si2PO12 (NZSP) faces challenges of high temperatures phase formation, larger particle size, and formation of secondary phases such as ZrO2 and Na2ZrSi4O11. This leads to Na and P loss, and poor density. Hence, it is difficult to achieve high ionic conductivity of NZSP ceramics. This study focuses on synthesizing NZSP powder via solution-combustion method to lower the phase formation temperature, enabling the fabrication of dense ceramics at reduced temperatures. The impact of metal ions: citric acid ratio, calcination temperature and time, on nature of combustion, phase evolution, particle size, and densification was investigated. Minimum ZrO2 impurity was observed at 1:2.5 M/C ratio, at calcination temperature of 1100oC for time of 12 h with particle size of 200-300 nm. Optimal results were achieved with sintering at 1225°C, resulting in 93.5% relative density and a total conductivity of 1.16 × 10−4 S cm−1 at room temperature. The enhanced ionic conductivity is attributed to the increased NASICON phase content and high relative density